1. Field of the Invention
The present invention relates to a switch gear, and more particularly to an improved multi-circuit switch gear which guides a current discharge operation to occur in the insulation gas provided in a main body during an earth operation at a designated interval of a power distributing line, thereby securing workers' safety and facilitating an earthing operation with regard to an underground insulation cable.
2. Description of the Background Art
A general multi-circuit switch gear is used for a power distribution system including an overhead power distributing line and an underground power distributing line, and allows an electrical power to apply therethrough to power receiving devices for a plurality of power consumers.
As shown in FIGS. 1 and 2, such a conventional multi-circuit switch gear is provided with: a main body 10 in which a power switching operation is carried out; a plurality of main bushings 20 including a plurality of input bushings 20a disposed at a portion of the main body 10 and receiving power therethrough and a plurality of output bushings 20b for supplying the power received through the input bushings 20a to respective power consumers.
A plurality of cables 30 for allowing the power to flow to and from the main bushings 20 are correspondingly connected to terminal connection kits 40 which are coupled to the main bushings 20.
A plurality of manipulating handles 50 are disposed at an upper portion of the main body 10 so that a switching actuator (not shown) provided in the main body 10 may be manually operated for switching a position of a conductor in the switch gear.
With reference to FIGS. 3A and 3B, the structure and operation of the terminal connection kits 40 connected to the main bushings 20 will now be described.
Into the terminal connection kits 40, the main bushing 20 provided at the main body 10 is inserted into an end portion of a T-type elbow valve connector 60, and a connection terminal 61 coupled to a cable adaptor 62 is inserted up into another end portion of the T-type valve connector 60 coupled thereto by the main bushing 20, whereby the connection terminal 61 is coupled to the main bushing 20.
A connection plug 63 is horizontally inserted into a third end portion of the elbow connector 60 which receives the main bushing 20 and the connection terminal 61, and the main bushing 20 connected to the connection terminal 61 therein receives therein an end portion of the connection plug 63. Another end portion of the connection plug 63 is housed in an insulation cap 64.
As shown in FIG. 4, the circuit composition of the conventional multi-circuit circuit switch gear will now be explained.
First, a circuit under a three-phase input/output pattern may vary from other switch gear circuits to, so that although circuit compositions of (A.sub.1, B.sub.1, C.sub.1), (A.sub.2, B.sub.2, C.sub.2)! will be described below, but others such as (A.sub.3, B.sub.3, C.sub.3), (A.sub.4, B.sub.4, C.sub.4), (A.sub.*, B.sub.*, C.sub.*)! are known in the art. Here, * denotes a natural number.
The circuit of the conventional multi-circuit switch gear includes a 2-position contact for supplying and breaking the power. An input unit (A.sub.1, B.sub.1, C.sub.1) with regard to respective phases A, B, C is formed into a single circuit, and respective output units (A.sub.2, B.sub.2, C.sub.2), (A.sub.*, B.sub.*, C.sub.*) are formed into other circuits.
As shown in FIGS. 5A and 5B, a breaking operation of the conventional multi-circuit switch gear for performing a maintenance or regular checkup by interrupting an electrical flow will now be explained. Here, 20a First, 22 denotes an opposite end portion of the main bushing disposed in the main body 10.
By an interruption operation of the manipulating handle 50 in order to break a current flow in the multi-circuit switch gear, a movable contact 66 is separated from a fixed contact 65 as shown in FIG. 5A, thereby activating the current interruption.
However, although the current flow from the main body 10 is interrupted, there remains, in the main bushing 20, a charged current that come in from the cable 30 connected to an exterior of the main body 10.
As shown in FIGS. 6A and 6B, an earthing operation for earthing the charged current remaining will now be described.
First, a connection plug 63 is externally exposed by removing an insulation cap 64 covering an end portion of the elbow connector 60 by use of an insulation stick 67.
Then, a protrusion 70a extended from an end portion of an earthing elbow 70 is momentarily inserted into an insertion hole (not shown) formed in an end portion of the exposed connection plug 63, thereby completing the earthing operation.
However, the conventional multi-circuit switch gear employs a two-position operation method according to its switching operation, so that it is required to disassemble the terminal connection kit while earthing the cable.
Further, there may occur a safety accident to a worker while an arc discharge is being carried out at an end portion of the cable through the terminal connection kit in the air.